Ancillary tool for fitting an ulnar component and/or a radial component of an elbow prosthesis

ABSTRACT

This ancillary tool ( 10 ) comprises a guide ( 30 ) for cut-out of the ulna (C) and/or the radius (R) intended to be positioned with respect to a trial humeral trochlea ( 20   2 ) belonging also to said ancillary tool and representative of the anatomical humeral trochlea when this trial trochlea is in place with respect to the corresponding cubital (S C ) and/or radial (S R ) articular surfaces.  
     This guide is also adapted to be positioned with respect to the ulna (C) and/or to the radius (R) equipped with this trial trochlea ( 20   2 ).

[0001] The invention relates to an ancillary device for fitting an ulnar component and/or a radial component of a total or partial elbow prosthesis.

[0002] An elbow prosthesis, such as known from EP-A-1 051 954, comprises an ulnar component and a radial component which must reproduce the ulnar and radial articular surfaces. The positioning of these surfaces with respect to the joint, particularly with respect to the humeral trochlea, is essential for the elbow thus fitted out to function well.

[0003] Up to the present time, surgeons implant the ulnar and radial components of elbow prostheses after having dislocated the joint and by attempting to reproduce the anatomical configuration of the articular surfaces. It happens that such reproduction is not perfect, hence a poor cooperation of the ulnar and/or radial articular surfaces with the humeral trochlea. This leads to premature wear of these surfaces and to discomfort for the patients.

[0004] It is a particular object of the invention to overcome these drawbacks by proposing an ancillary fitting tool which allows precise positioning of the ulnar component and/or of the radial component with respect to the humeral trochlea, which substantially improves the functional conditions of the elbow thus fitted out.

[0005] In this state of mind, the invention relates to an ancillary tool for fitting an ulnar component and/or a radial component of a total or partial elbow prosthesis, which comprises a guide for cut-out of the ulna and/or radius, this guide being intended to be positioned with respect to a trial humeral trochlea belonging also to said ancillary tool and representative of the anatomical humeral trochlea, when the trial trochlea is in place with respect to the corresponding ulnar and/or radial articular surfaces. This guide is also adapted to be positioned with respect to the ulna and/or radius equipped with the trial trochlea.

[0006] Thanks to the invention, the guide enables the surgeon to mark the zones of resection of the bone or bones, taking into account the real dimensions of the trochlea. In other words, the cut-out guide functions like a three-dimensional anatomical sensor of the surface of the trochea, which allows the zones of cut to be efficiently positioned with respect to this trochlea.

[0007] According to advantageous but non-obligatory aspects of the invention, the ancillary tool incorporates one or more of the following characteristics:

[0008] The guide comprises a support on which the trial trochlea may be mounted and on which are mounted screws adapted to bear against the ulna and/or the radius for immobilisation of the guide with respect to these bones.

[0009] The aforementioned support comprises a tab whose end forms a member for guiding a tool for cut-out of the upper end of the radius. This guiding member may comprise a slot for slide of a blade for resection of the upper end of the radius.

[0010] The aforementioned support forms a cylindrical member for guiding a bell-shaped saw for the preparation of the upper end of the ulna.

[0011] The aforementioned support comprises a tab which supports a shaft on which the trial trochlea may be mounted. In that case, the axes of symmetry of the cylindrical member for guiding the bell-shaped saw and of the shaft on which the trial trochlea may be mounted, are advantageously merged, the aforementioned shaft being hollow and forming a volume for slide and guiding of a central pin of the bell-shaped saw.

[0012] The afore-mentioned support extends in a rod adapted to be positioned, over the major part of its length, parallel to the patient's fore-arm. This rod allows the surgeon to rapidly pre-position the support before a fine adjustment obtained thanks to the aforementioned screws.

[0013] The support is formed by assembling a plurality of pieces selected as a function of the size of the trial trochlea. In other words, the geometry of the support depends on the size of the trial trochlea, i.e. in fact on the size of the anatomical trochlea of which the trial trochlea is a three-dimensional representation. This adaptation to the size of the anatomical trochlea allows a corresponding adaptation of the ulnar and radial cut-out zones.

[0014] A guiding tool is provided for boring the ulna, this tool comprising a template adapted to abut against the cut-out surface of the olecranon, this template being provided with a bore for guiding a drill or the like, while this template is fast with a handle for adjusting its angular position with respect to a central axis of the cut-out surface.

[0015] The invention allows an ulnar component or a radial component of an elbow prosthesis to be fitted in accordance with a method which comprises steps consisting in positioning a cut-out guide with respect to a trial humeral trochlea representative of the anatomical humeral trochlea, when the trial trochlea is in place with respect to the corresponding ulnar and/or radial articular surfaces, in immobilising this guide with respect to the ulna and/or radius and in cutting out the ulnar and/or radial upper ends in function of profiles defined by this guide.

[0016] It may, in addition, be provided to cut out the ulna, forming a surface inscribed in a cylinder and centered on a geometric axis of the outer surface of the trial trochlea. In that case, the trial trochlea is advantageously maintained in position with respect to the ulna during cut-out thereof, cut-out being performed, at least in part, around this trial trochlea.

[0017] In addition, the ulna may be cut out by means of a bell-shaped saw guided in a member provided with a guiding ring coaxial with the trial trochlea.

[0018] Finally, according to an advantageous aspect of this method, the guide is immobilised with respect to the ulna thanks to three screws passing through a support of the guide and coming respectively into abutment on the olecranon, on the posterior planar triangle and on the lateral plane of the ulna.

[0019] The invention will be more readily understood and other advantages thereof will appear more clearly in the light of the following description of a form of embodiment of an ancillary tool in accordance with its principle and of its method of use, given solely by way of example and made with reference to the accompanying drawings, in which:

[0020]FIG. 1 is a view in perspective of an ancillary tool according to the invention during a first step of use, the ulna and the radius being shown in faint lines in order to render the drawing clearer.

[0021]FIG. 2 is a view in perspective of the ancillary tool of FIG. 1, during a second step of use.

[0022]FIG. 3 is a view similar to FIG. 1 during a third step of use.

[0023]FIG. 4 is a partial section along line IV-IV in FIG. 3.

[0024]FIG. 5 is a view in perspective of the upper ends of the radius and of the ulna, during a fourth step of use, and FIG. 6 is a view similar to FIG. 5 during the positioning of artificial components on the ulna and on the radius.

[0025] The ancillary tool 10 according to the invention is intended to be immobilised with respect to the ulna C and to the radius R of an elbow joint to be fitted out with an artificial ulnar component and/or an artificial radial component.

[0026] This ancillary tool comprises a plurality of trials of humeral articular assemblies 20 ₁, 20 ₂ and 20 ₃ which, for simplification, are called “trial humeral trochleas”, and which the surgeon can compare successively with the anatomical trochlea of the corresponding humerus or install in the sigmoidal cavity of the ulna. Of course, the number of trial trochleas is not limited to three and depends on the precision desired during this comparison.

[0027] The trochleas 20 ₁, 20 ₂, 20 ₃ are of symmetry of revolution and each provided with a central bore 21 allowing them to be assembled on a support 31 forming the reinforcement of a cut-out guide 30 belonging to the ancillary tool 10.

[0028] The support 31 is formed by mechanical assembling of a plurality of metallic pieces. More precisely, the support 31 comprises a U-shaped stirrup element 32 on which is mounted a hollow shaft 33 which may be inserted in the bore 21 of the trial trochlea selected.

[0029] It is assumed in the following that trochlea 20 ₂ has been selected by comparison with the anatomical trochlea.

[0030] This trochlea is then placed in abutment against the inner surface S_(C) of the olecranon and the articular surface S_(R) of the radial head, in a position close to that of the anatomical trochlea before dislocation of the elbow.

[0031] The shaft 33 is mounted on a first arm 34 of the stirrup element 32. The second arm 35 of the stirrup element 32 terminates in a ring 36 of which 1 ₃₆ denotes the width. The ring 36 and the hollow shaft 33 are coaxial and centered on an axis X-X′ which is also the axis of symmetry of the trial trochlea 20 ₂ mounted on the support 31.

[0032] The support 31 also comprises a tab 37 immobilised on the support 31 and which comprises two arms 37 a and 37 b substantially perpendicular to each other, the arm 37 b comprising at its free end a guide 37 c defining a slot 37 d substantially parallel to axis X-X′.

[0033] The stirrup element 32 also supports a second tab 38 fixed on the stirrup element 31 and which comprises two arms 38 a and 38 b substantially perpendicular to each other. The arm 38 b is equipped with a carriage 39 fast with a rod 40, the carriage 39 being able to slide with respect to the arm 38 b as represented by the double arrow F₁ in FIG. 1.

[0034] The arm 38 a is provided with a boss 38 c in which is formed a tapping for receiving a screw 41 intended to come into abutment against the proximal part of the olecranon.

[0035] As for the carriage 39, it is equipped with a screw 42 intended to come into abutment against the posterior planar triangle of the ulna.

[0036] Finally, the ring 36 is provided with an extension 36 a in which is screwed a screw 43 intended to come into abutment against the lateral plane of the ulna.

[0037] The cut-out guide 30 is placed in position with respect to the ulna C and to the radius R by arranging the rod 40 substantially along the patient's fore-arm then by screwing the screws 41 to 43 more or less, with the result that the trial trochlea 20 ₂ is positioned with respect to the ulnar (S_(C)) and radial (S_(R)) articular surfaces substantially in the same way as the anatomical trochlea when the elbow is not dislocated. When this position is attained, the screws 41 to 43 are screwed, so that the guide 30 is immobilised with respect to the ulna, and therefore with respect to the radius.

[0038] In this position and as shown in FIG. 2, it is possible to introduce a blade 50 in the slot 37 d so as to cut the upper end of the radius R. The position of the line of cut of the radius R is determined by taking into account the height of the radial knob which will be subsequently positioned on the radius. This guarantees that the articular surface of this radial knob will be correctly positioned with respect to the trochlea with which it must cooperate.

[0039] In FIG. 2, arrows F₂ and F₃ represent the directions of introduction and of reciprocating movement of the blade 50 with a view to cutting out the radius R.

[0040] As is more particularly visible in FIGS. 3 and 4, it is then possible to introduce a bell-shaped saw 60 in the ring 36, parallel to axis X-X′ and as represented by arrow F₄. The bell-shaped saw 60 is equipped with a central guiding finger 61 aligned on axis X-X′ and whose diameter allows it to penetrate in the inner volume 33 a of the shaft 33, which makes it possible to efficiently guide the tubular saw 60 in cooperation with the inner bearing surface of the ring 36 which extends over its width 1 ₃₆.

[0041] The bell-shaped saw makes it possible to cut out the olecranon of the ulna C around the trial trochlea, creating a cylindrical surface portion with circular base S, more particularly visible in FIG. 5.

[0042] When the radius and the ulna have been cut out, the cut-out guide 30 is removed by unscrewing screws 41 to 43 and the bones can be prepared for receiving the artificial components.

[0043] A bore R₁ in the radius R is made substantially along the axis of the neck of the radius, while a guiding tool 70 is used for determining the direction of a bore C₁ to be performed in the ulna for receiving the anchoring shank 101 of an artificial ulnar component 100. The tool 70 comprises a template 71 provided with a bore 72 for receiving and guiding a drill 73, a punch or a suitable cut-out tool. The outer surface 74 of the template 71 is a portion of cylindrical surface with the same radius as the surface S and the template 71 may pivot about axis X-X′ which is the axis of symmetry of the surface S.

[0044] In order to control the angular positioning of the template 71 with respect to axis X-X′, i.e. the direction of the bore 72 with respect to the ulna C, the template 71 is connected by a shaft 75 to a handle 76 intended to be held by the surgeon or one of his/her assistants and allowing an effort of tipping F₅ of the template 71 about axis X-X′ to be exerted.

[0045] It will be understood that, when the template 71 is in contact with the surface S, it is possible to create the bore C₁ by introducing the drill 73 in the bone through the bore 72, as schematically represented by arrow F₆.

[0046] When the bores C₁ and R₁ have been made, the ulnar component 100 can be positioned by introducing its anchoring shank 101 in the bore C₁, while a radial knob 110 can be positioned on the radius R by introducing its anchoring shank 111 in the bore R₁.

[0047] Thanks to the invention, it is possible to position components 100 and 110 correctly by taking into account the combined anatomy of the ulna, the radius and the humerus as, in the configuration of FIG. 1 which determines the positioning of the guide 30 and the cutting zones, the trial trochlea is in abutment on the anatomical articular surfaces of the ulna and the radius. This results in a precise positioning of these components, with a correct ligamentary balance of the joint.

[0048] The invention has been described for positioning an ulnar component and a radial knob, but it may, of course, be used for positioning one of these components only.

[0049] The invention has been described for use via a firstly lateral approach, in particular for access of the bell-shaped saw 60 via the lateral side of the joint. A firstly medial approach may, of course, be used, with an ancillary tool designed symmetrically with respect to that shown in the Figures. 

1. Ancillary tool for fitting an ulnar component and/or a radial component of a total or partial elbow prosthesis, characterized in that it comprises a guide for cut-out of the ulna (C) and/or radius (R), intended to be positioned with respect: to a trial humeral trochlea belonging also to said ancillary tool and representative of the anatomical humeral trochlea, when said trial trochlea is in place with respect to the corresponding ulnar (S_(C)) and/or radial (S_(R)) articular surfaces, and to the ulna (C) and/or radius (R) equipped with said trial trochlea.
 2. Ancillary tool according to claim 1, characterized in that said guide comprises a support on which may be mounted said trial trochlea and on which are mounted screws adapted to come into abutment against the ulna (C) and/or the radius (R) for immobilising said guide with respect to said bones.
 3. Ancillary tool according to claim 2, characterized in that said support comprises a tab of which the end forms a member for guiding a tool for cutting out the upper end of the radius (R).
 4. Ancillary tool according to claim 3, characterized in that said guiding member comprises a slot for slide (F₂, F₃) of a blade for resection of the upper end of the radius (R).
 5. Ancillary tool according to claim 2, characterized in that said support forms a cylindrical member for guiding a bell-shaped saw for preparation of the upper end of the ulna (C).
 6. Ancillary tool according to claim 2, characterized in that said support comprises a tab which supports a shaft on which said trial trochlea can be mounted.
 7. Ancillary tool according to claim 4, characterized in that the axes of symmetry (X-X′) of said cylindrical guiding member and said shaft merge, said shaft being hollow and forming a volume for slide and guide of a central axis of said bell-shaped saw.
 8. Ancillary tool according to claim 2, characterized in that said support extends in a rod adapted to be positioned, over the major part of its length, parallel to the patient's fore-arm (C, R).
 9. Ancillary tool according to claim 2, characterized in that said support is formed by assembling of a plurality of pieces selected as a function of the size of said trial trochlea.
 10. Ancillary tool according to claim 1, characterized in that it comprises a guiding tool for boring the ulna (C), said tool comprising a template adapted to come into abutment against the cut-out surface (S) of the olecranon, said template being provided with a bore for guiding a drill or the like, while said template is firmly attached with a handle for adjusting the angular position of said template with respect to a central axis (X-X′) of said cut-out surface.
 11. Method for fitting an ulnar component and/or a radial component of a total or partial elbow prosthesis, characterized in that it comprises the steps consisting in: positioning a cut-out guide with respect to a trial humeral trochlea representative of the anatomical humeral trochlea, when said trial trochlea is in place with respect to the corresponding ulnar (S_(C)) and/or radial (S_(R)) articular surfaces, immobilising said guide with respect to the ulna and/or radius, and cutting out (F₂, F₃, F₄) the ulnar and/or radial upper ends as a function of profiles defined by said guide.
 12. Method according to claim 11, characterized in that it comprises a step consisting in cutting out the ulna, forming a surface inscribed in a cylinder and centered on a geometric axis (X-X′) of the outer surface of said trial trochlea.
 13. Method according to claim 12, characterized in that said trial trochlea is maintained in position with respect to the ulna (C) during cut-out (F₄) of the ulna, said cut-out (F₄) being effected, at least in part, around said trial trochlea.
 14. Method according to claim 12, characterized in that the ulna may be cut out (F₄) by means of a tubular saw guided in a member provided with a guiding ring (36) coaxial (X-X′) with said trial trochlea.
 15. Method according to claim 11, characterized in that said guide is immobilised with respect to the ulna thanks to three screws passing through a support of said guide, and coming respectively into abutment on the olecranon, on the posterior planar triangle and on the lateral plane of the ulna (C). 